Japanese Patent Application Laid-open Publication No. 2007-249729, for example, describes a storage system including multiple microprocessors, which is designed to prevent load concentration on one microprocessor. In this storage system, when a microprocessor that performs I/O processing in response to an I/O request received from an upper-level apparatus has a load higher than a predetermined load, the microprocessor causes another microprocessor to execute the high-load part of the I/O processing.
In a storage apparatus including multiple microprocessors, it is necessary to properly manage control information in the microprocessors. Especially when such control information is frequently updated, it is necessary to reduce an influence (overhead) on a host apparatus, which is caused by processing for updating the control information.